The present invention relates generally to a manner by which to handover communication with a mobile Bluetooth-compatible (BT), or other communication, device from an active communication device to a target communication device. More particularly, the present invention relates to a method, and an associated apparatus, for facilitating handover of communications of the mobile Bluetooth, or other, device from an active piconet to a target piconet. Handover of communications is possible in a Bluetooth scatternet which lacks a fixed infrastructure as well as a Bluetooth system having access points forming a fixed infrastructure, or a combination thereof.
The use of multi-user radio communication systems has achieved wide popularity in recent years as advancements in communication technologies have permitted the affordable utilization of such communication systems by large numbers of users to communicate therethrough.
Like other types of communication systems, a radio communication system is formed, at a minimum, of a sending station and a receiving station interconnected by way of a communication channel. In a radio communication system, the communication channel is formed of a radio communication channel. A radio communication channel is defined upon a portion of the electromagnetic spectrum. A communication channel defined in a wireline communication system, in contrast, is defined upon a wireline connection extending between the sending and receiving stations. Because a radio communication channel defined upon a portion of the electromagnetic spectrum is used to communicate communication signals between the sending and receiving stations, the need for wireline connection between the sending and receiving stations of a conventional wireline communication system is obviated. The use of a radio communication system to communicate therethrough, as a result, inherently increases the mobility of communication relative to communications in a conventional wireline communication system.
Digital communication techniques have been implemented in radio, as well as other, communication systems. Digital communication techniques generally permit the communication system in which the techniques are implemented to achieve greater communication capacity contrasted to conventional, analog communication techniques.
In a communication system which utilizes digital communication techniques, information which is to be communicated is digitized to form digital bits. The digital bits are typically formatted according to a formatting scheme. Groups of the digital bits, for instance, are positioned to form a packet of data.
Because packets of data can be communicated at discrete intervals, rather than continuously, a frequency band need not be dedicated solely for the communication of data between one communication pair. Instead, the frequency band can be shared amongst a plurality of different communication pairs. The ability to share the frequency band amongst the more than one communication pair permits a multiple increase in the communication capacity of the system.
Packet-data communications are effectuated, for instance, in conventional LAN (Local Area Networks). Wireless networks, operable in manners analogous to wired LANs, referred to as WLANs (Wireless Local Area Networks) have also been developed and are utilized to communicate data over a radio link. Some of such systems are able to provide for voice, as well as non-voice, communications.
A communication standard, referred to as Bluetooth, has been promulgated which provides a standard operating protocol by which to communicate data over a relatively short distance, e.g., about ten meters. The Bluetooth communication standard provides a manner which enables seamless voice and data communication by way of short-range radio links and permits a broad range of devices to be connected easily and quickly by way of the radio links. Proposals have been set forth to provide a wide array of devices with Bluetooth communication capabilities. Mobile computers and mobile phones are exemplary of devices which have been proposed to make use of the Bluetooth communication standard.
An advantageous characteristic of the Bluetooth communication standard is the ability to provide combined usability models based upon functions provided by different devices. For instance, using Bluetooth-based communication signals, a communication path can be formed between a PDU (Personal Data Unit) and a cellular phone. And, a second communication path is also formable between a cellular phone and a cellular base station, thereby providing connectivity for both data and voice communication. In this exemplary implementation, the PDU maintains its function as a computing device and the cellular phone maintains its function as a communication device, while each of the devices provides a specific function efficiently by way of the Bluetooth communication scheme.
Multi-point connections are also provided through the use of a Bluetooth-based communication scheme. While the radio range envisioned pursuant to the Bluetooth communication standard is relatively small, i.e., on the order of ten meters, Bluetooth-based devices can, appropriately positioned, act as bridges to extend the range of the communication of the Bluetooth-based communication signals.
A WIO (Wireless Intranet Office) is also exemplary of a communication system in which Bluetooth-compatible devices can be utilized. In a WIO, typically, voice, and other real-time, communications are provided through the use of a mobile station. Voice communication by way of a WIO provides the advantages of use of a wireless communication system in a cost-effective manner. Voice, as well as other data, can be communicated between mobile stations operable in such a system.
The Bluetooth communication standard defines a piconet, formed of two or more Bluetooth-compatible devices which share a common communication channel. In a WIO or WLAN, the piconet architecture defined in the Bluetooth communication standard is integrated into the WLAN through the introduction of an access point (AP). An access point defines a logical point at which data unit of the wired portion of the LAN enters the piconet defined in the Bluetooth communication standard.
By positioning a plurality of access points at a plurality of spaced-apart locations, a mobile station exiting a communication range encompassed by a first access point enters the communication range encompassed by a second access point.
Analogous to operation of a mobile station in a conventional, cellular communication system in which communication handovers are effectuated to permit continued communication by the mobile station as the mobile station moves throughout a geographical area, a mobile station operable in the LAN similarly would be permitted continued communication if handover of communications between access points would be possible.
While currently, the Bluetooth communication standard does not define a handover method, a manner by which to handover communications of a mobile station from one piconet to another would advantageously facilitate communications in a Bluetooth-compatible communication system.
It is in light of this background information related to wireless communication systems that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides a method, and associated apparatus, by which to handover communications with a mobile communication device, such as a mobile Bluetooth-compatible device, or other communication device, from an active communication device to a target communication device.
Through operation of an embodiment of the present invention, handover of communication is possible between Bluetooth scatternets, or other networks which lack fixed infrastructures. Handover of communications is also possible in a Bluetooth, or other, system having access points forming a fixed infrastructure, as well as also in a system having both scatternets and a fixed infrastructure.
In one aspect of the present invention, apparatus, and an associated method, is provided by which to handover communications with a mobile Bluetooth from one piconet to another in a manner both to permit continued communication as well as to limit packet loss during the handover.
When handover is to be effectuated between successive access points of a Bluetooth-compatible WLAN, the mobile Bluetooth device forming the mobile station is initially a slave to the access point with which the mobile Bluetooth device communicates. When the mobile Bluetooth device travels into an area encompassed by another access point, a handover of communications from the first access point to the subsequent access point is generally desired. Measurements are performed during operation of the mobile Bluetooth device. For example, measurements are made to determine when a handover should be initiated. In one implementation, power levels, or other of the signals detected at the Bluetooth device communication quality indicia, are measured at selected intervals.
When the power levels of signals generated by the first access point falls beneath a certain threshold, the Bluetooth mobile device sends an inquiry message to the second access point, forming now a target access point. The inquiry message inquires of a device address associated with the target access point. When the target access point receives the inquiry, a response is generated, and returned to the mobile Bluetooth device, with the appropriate address and clock information of the target access point. Thereafter, the target access point pushes other Bluetooth devices in the piconet in which the target access point also forms a portion, into reduced-power states, such as SNIFF or HOLD states. If the availability of temporary addresses by which to identify the mobile Bluetooth device is limited, one or more of the other Bluetooth devices associated with the second piconet can be put into a PARK mode by the target access point. When pushed into a PARK mode, the temporary address identifying such Bluetooth device is made available to identify other Bluetooth devices, such as the mobile Bluetooth device of which handover of communications is desired.
In another aspect of the present invention, the master-slave roles of the target access point and the mobile Bluetooth device are exchanged. That is to say, with respect to each other, the mobile Bluetooth device becomes a master and the target access point becomes a slave thereto. The mobile Bluetooth device, prior to the handover, remains as a slave to the access point associated with the first piconet. Time synchronization of the target access point to the mobile Bluetooth device is then effectuated. Because of the time synchronization, the handover of communications from the first piconet to the second piconet can be effectuated without loss of packets of data during the handover due to non-synchronization of timing between the piconets.
In another aspect of the present invention, when selection is made is initiate a handover, the active access point is caused to push all active Bluetooth devices, other than the mobile Bluetooth device and the active access point, into reduced power-level states. Then, the mobile Bluetooth device and the active access point exchange master-slave roles. That is to say, the mobile Bluetooth device becomes a master to the active access point, and the active access point becomes a slave thereto. Thereafter, handover is effectuated of the mobile Bluetooth device from the first piconet to the second piconet and the connection of the mobile Bluetooth device to the first piconet is terminated.
In another aspect of the present invention, handover of communications is effectuated between piconets of a scatternet. Handover of communications is effectuated with a handover of communication from a first piconet to a second piconet. The mobile Bluetooth device and a master device of the second piconet exchange master-slave relationships with respect to each other. Once the mobile Bluetooth device becomes a master with respect to the device which becomes its slave, the mobile Bluetooth device causes such other device to become time synchronized thereto. Thereafter, handover of communications to the second piconet is effectuated.
Because a manner is provided by which to facilitate handover of communications between piconets of a Bluetooth communication system, the convenience of use of the Bluetooth communication system is facilitated.
In these and other aspects, therefore, a method, and associated apparatus, is provided for handing over communications of a mobile communication device initially operable in a connected state in a first piconet to a second piconet, thereafter to be operable in a connected state in the second piconet. The first piconet includes at least one first-piconet communication device and the second piconet includes at least one second-piconet communication device. The initiation of handover of communications from the first piconet to the second piconet is selected responsive to communication indicia representative of communications with the mobile communication device. The at least one second-piconet communication device is caused to be come time-synchronized with the mobile communication device. Thereafter, communications with the mobile communication device by way of the second piconet is effectuated. Thereby, the mobile communication device is operated in the connected state in the second piconet.
A more complete appreciation of the present invention and the scope thereof can be obtained from the accompanying drawings which are briefly summarized below, the following detailed description of the presently-preferred embodiments of the invention, and the appended claims.